Enamels and process of making them.



UNITED STATES PATENT max MAYER, or TEMPELHOF, AND BELA HAvAs'or scnolvnnnne, u man;

GERMANY, ASSIGNORS TO CHEMISCH-METALLURGISCHE INDUSTRIE GESELL- SGHAFT MIT-BESCHRANKTER HAFTUNG, OI BERLIN, GERMANY, A COB-PORLTIQN or GERMANY,

ENAMELS m) rnocnss or mxme rnmr.

No Drawing.

To all whom it may concern:

Be it known that we, MAX MAYER, a cit1- zen of the German Empire, and resident of Tempelhof, near Berlin, Germany, and BELA HnvAs, a citizen of the Kingdom of Hungary, and resident of Schtineberg, near Berlin, Germany, have jointly invented certain-new and useful ImprovementsinEnamels and Processes of-MakingThem.

Stannic oxid, added to the enamel before or during the grinding operation, has been used hitherto exclusively for the purpose of giving enamel an opaque white color. Attempts made so far to find substitutes for stannic oxid which would be cheaper yet just as efiicient, have generally failed to yield commercially available results.

In Tscheuschners Glas Fabm'lcation 5th edition 1885, page 552, and in Wilkens- Schumachers Die Kemmz'schen Ton/fabrilcate 5th edition, 1884, page 189, We find statements to the effect that opaquing properties have been ascribed to sodium aluminate and to alumina. It should be borne in mind, however, that a substance having theproperty of giving a White color, to a glass melt, Wll]. by no means in every case be suitable for giving an opaque white color to enamel. For the latter purpose the substance must not onlyhave the requisite opaquing property, but it must also to a cer-' tain degree, enter into reaction with the socalled covering enamel and yield a smooth surface. I

Our experiments have shown-that the ad dition of sodium aluminate to enamels doesnot give themfany opaque tint worth mentioning, whether the aluminat'e be used in the crude state or after preliminary heating. In either case, an almost transparent molten; mass is obtained. Pure aluminum oxid yields about the same result if used without heating (calcining). With pure aluminum oxid sub ected to a preliminary heating it is indeed possibleto obtain opaque tinted-or white enamel, but only by using the oxid in so large quantities that the surface becomes rough and thus utterly unsuitable for enamel work. The reason for this failure is that calcined "aluminum oxid also fails to dissolve in the glass melt to the degree required'forthe production of a thoroughly opaque enamel'having a smooth surface.

. sium spiuel) resp. ZnOAl O which will: be probably to a Magnesium oxid, which a-lso'is of a pure white color has not been proposed hitherto as an opaquin-g agent for enamel, and experiments made bv us showed that it is contained in all the calcined mixtures.

The opaquing eflect produced on enamels is increased by, using calcined mixtures of aluminum oxid and magnesium oxid or aluminum oxid and zinc oxid to which hasbeen added before calcining stannic oxid, zirco-- nium oxid, titanic oxid, silicic oxid or other white refractory materials or mixtures of such substances. Opaquing eifects materially stronger than those obtained with the pure mixtures alone are obtained even with additions of only 10% of the amount of the-mix ture of aluminum oxid and magnesium oxid.

The effect observed is such that it cannot 'be considered amere sum of the individual ef-'..- fects. It is not clear whetherthese additi'ons simply increase the opaquing effect or whether they also improve the capacity of the opaquing agent'for distributing itself in .the channel.

Notonly calcined mixtures of aluminum oxid and magneslum. oxid but as already mentioned calcined mixtures of zinc oxid and aluminum oxid likewise are suitable for use as an. opaquing agent according to our. 'mventlon. The poisonous nature ofthese mixtures, however, prohibits .their use in some cases, and we intend to us'e'them chiefly for so-called cosmetic (decorative) enamels.

Our invention is of: great commercial value, as will be obvious upon considering that the calcined mixtures can beroduced', much more cheaply than stannic-oxid, which is the only agent used hitherto o'h'a large scale for hygienic enamels. Even when the OFFICE.

certain degree Specification of Letters Patent. Patented July 21, 1914, Application filed November 19,1312. Serial 0. 732,216.

additions named above are used to increase the opaquing eiiect, the saving is quite considerable as compared with the employment of stannic oxid.

When in the claims, we use the word spinel we wish it to be understood that we desire thus to specify, either a mixture of magnesium oxid and aluminum oxid said mixture having been previously calcined at such high temperatures as to form magnesium spinel, or a mixture of zinc oxid and aluminum oxid said mixture having been previously calcined at such high temperatures as to form zinc spinel.

lVe claim as our invention:

1. The process of producing white opaque enamels, which consists in adding to the enamel proper a white opaquing agent containing spinel.

2. The process of producing white opaque enamels, which consists in adding to the enamel proper a white opaquing agent containing spinel and a suitable white refractory material.

3. A white opaque enamel comprising a body of enamel proper containing spinel as the whitely opaquing medium.

'4. A white opaque enamel comprising in addition to the enamel proper, a suitable white refractory materialjnnd spinel as the whitely opaquing medium.

In witness whereof we have hereunto set 'our hands in the presence of two subscribing witnesses.

MAX MAYER. BELA HAVAS. Witnesses:

HENRY HASPER,

WOLDEMAR HAUPT. 

